The Radiative Budget of an AtThe Radiative Budget of an Atmospheric Column in Tropical mospheric Column in Tropical

Western PacificWestern Pacific

Zheng LiuZheng LiuDepartment of Atmospheric ScienceDepartment of Atmospheric Science

University of WashingtonUniversity of Washington

BackgroudBackgroud

► Cloud and cloud-radiation parameterization determines the Cloud and cloud-radiation parameterization determines the cloud and water vapor feedback of climate model,which indcloud and water vapor feedback of climate model,which induce high sensitivity to the forcing variationuce high sensitivity to the forcing variation

► Model evaluation: TOA, surface radiative budgets and the cModel evaluation: TOA, surface radiative budgets and the column absorption, heating rate profileolumn absorption, heating rate profile

► Limited measurements: start with some atmospheric columLimited measurements: start with some atmospheric columns, Manus and Nauruns, Manus and Nauru

Data Set Description: Data Set Description: Observational DatasetObservational Dataset

► TOA SW net fluxes and LW fluxes:TOA SW net fluxes and LW fluxes: GMS hourly observati GMS hourly observations, 0.3ons, 0.3o o x 0.3x 0.3o o gridgrid

► Surface SW&LW downward fluxes:Surface SW&LW downward fluxes: ARM surface measur ARM surface measurements, daily averaged from 1-min data ements, daily averaged from 1-min data

► Surface LW upward fluxes:Surface LW upward fluxes: NOAA Optimum Interpolated NOAA Optimum Interpolated SST, weekly averaged, 1SST, weekly averaged, 1o o x 1x 1o o gridgrid

► Surface SW upward fluxes:Surface SW upward fluxes: assumed Sea Surface SW A assumed Sea Surface SW Albedo (6%) lbedo (6%)

Data Set Description: Data Set Description: Radiative Model CalculationsRadiative Model Calculations

► Computed fluxes and heating rates from ARM columComputed fluxes and heating rates from ARM column observationsn observations Retrieve vertical profiles of cloud microphysical properties Retrieve vertical profiles of cloud microphysical properties

from ARM millimeter wave radar datafrom ARM millimeter wave radar data

Temperature and water vapor profiles from radiosonde laTemperature and water vapor profiles from radiosonde launchesunches

Sample the cloud properties every 5 minutes and perform Sample the cloud properties every 5 minutes and perform radiative transfer only on the sampled profiles.radiative transfer only on the sampled profiles.

Calculate broadband fluxesCalculate broadband fluxes

Data Set Description: Climate ModelData Set Description: Climate Model

► NCAR Community Atmosphere Model (CAM)NCAR Community Atmosphere Model (CAM) T42 resolutionT42 resolution Prescribed SSTPrescribed SST Compare values from box over Manus (280 km x 280 kCompare values from box over Manus (280 km x 280 k

m) with observationsm) with observations

► Multi-scale modeling framework (MMF)Multi-scale modeling framework (MMF) Embedded 2D cloud system resolving model (64 columEmbedded 2D cloud system resolving model (64 colum

ns each 4 km in horizontal dimension)ns each 4 km in horizontal dimension) Prescribed SSTPrescribed SST Average 64 column values within Manus gridboxAverage 64 column values within Manus gridbox

Conversion to Daily Averaged Conversion to Daily Averaged FluxesFluxes

► Diurnal integration for SW: integrate the fluxes Diurnal integration for SW: integrate the fluxes from sunrise to sunset and averaged over the from sunrise to sunset and averaged over the dayday

► Interpolation of missing data: SW & LWInterpolation of missing data: SW & LW

► Discard days with more than four hours of Discard days with more than four hours of

missing datamissing data

Observation v.s. Radiative ModelObservation v.s. Radiative Model

► Comparison of frequency distributionComparison of frequency distribution

► Comparison of daily averaged fluxesComparison of daily averaged fluxes

► SW & LW; clear sky & all sky; TOA, surface and cSW & LW; clear sky & all sky; TOA, surface and column absorptionolumn absorption

► Take the same time period for observations and raTake the same time period for observations and radiative model calculations: about 110 days’ data fodiative model calculations: about 110 days’ data for each site r each site

Observation v.s. Climate ModelObservation v.s. Climate Model

► Observation: Jun 16, 1999 ~ May 21, 2003Observation: Jun 16, 1999 ~ May 21, 2003

► Climate Model: Jan 1, 1999 ~ Dec 31, 1999Climate Model: Jan 1, 1999 ~ Dec 31, 1999

ConclusionConclusion

► Column SW absorption:Column SW absorption: Clear sky: around 90w/mClear sky: around 90w/m22

All sky:All sky: almost unaffected by cloud for both radation model and clialmost unaffected by cloud for both radation model and cli

mate modelmate model much greater variation according to observational data anmuch greater variation according to observational data an

d bias towards more absorption than clear skyd bias towards more absorption than clear sky► Discrepancy with observations probably due to scene Discrepancy with observations probably due to scene

mismatch between TOA and the surface and some 3D mismatch between TOA and the surface and some 3D effects effects

► Evaluation of the radiative budget of atmospheric coluEvaluation of the radiative budget of atmospheric columns can help understand the convective tropicsmns can help understand the convective tropics

Future workFuture work

► Compare with other TOA satellite data sets: ISCCompare with other TOA satellite data sets: ISCCP, CERESCP, CERES

► Compare budget results from CAM run in forecaCompare budget results from CAM run in forecast mode with data and climate model version of st mode with data and climate model version of CAMCAM

► Surface radiative budget from satellite with ARM Surface radiative budget from satellite with ARM surface measurementsurface measurement

Thanks toThanks to

► Professor AckermanProfessor Ackerman► Sally Mcfarlane, Professor Fu, Professor WoodSally Mcfarlane, Professor Fu, Professor Wood► All my first year classmatesAll my first year classmates► All the audience here All the audience here